Irradiation effects on the tensile properties of LONGLIFE materials irradiated in the BR2 (SCK-6, FZD-1a and FZD-1b)

Three RPV steels from the LONGLIFE material list, namely, SCK–6 (22NiMoCr37), FZD–1a (JPB) and FZD–1b (JPC) were irradiated in the BR2 reactor at 290°C to five different fluence levels ranging from about 6 E18 to 1.6 E20 n/cm² , E>1MeV. Tensile specimens were tested at room temperature to determine the irradiation–induced hardening with the accumulated neutron exposure. The results show that for the three materials, there is a monotonic increase of hardening with neutron fluence. None of the steels showed any acceleration of embrittlement or late blooming phenomenon leading to damage rate increase. Various embrittlement trend curve formulas were applied to these steels, in particular the EONY formulation to be included in the US Reg. Guide 1.99 revision 3, the revised French FIM formulation and the revised Japanese JEAC–4201 formulation. The EONY formulation clearly underestimates the actual hardening mainly because of the low-Cu content of the materials. The high P steel, FZD–1a, irradiation hardening is underestimated by all formulations. On the other hand, good agreement is obtained for FZD–1b plate with all formulations. Finally, it is found that the two JEAC–4201 and FIM formulations lead to very similar results up to about 1 E20 n/cm².